Energized liquid developers for developing electrostatic images

Abstract

A method of developing electrostatic images in which a liquid developer is maintained in quiescent condition in contact with the base material carrying the electrostatic image and wherein the developer contains in separate coexistence within an insulating carrier liquid toner particles of relatively low dielectric constant and movement-inducing particles having a high dielectric constant. The presence of both sets of particles results in agitation in the liquid due to particle movement in a field by charge exchange between the high dielectric particles and the other particles to produce random agitation of the particles in the liquid and thereby high mobility of the toner particles during developing.

We claim: 
     
       1. A method of developing electrical field images which comprises applying a developer to a base material having a coating comprising a photosensitive medium and a resin having embedded therein particulate conductive particles or a medium which increases the conductivity in the proportion by weight of 100 to 500 grams of resin to 0.5 to 2 grams of conductive material to form a membrane capable of sustaining a latent electrostatic image, said developer being an energized liquid developer comprising in separate co-existence within an insulating liquid of (a) toner particles of relatively low dielectric constant arranged due to their electrical characteristic to deposit on selected image areas and (b) movement-inducing high dielectric constant metallic powder particles which have a rapid charge exchange with other particles and adjacent surfaces to cause the said high dielectric particles to oscillate between other particles and the said surfaces whereby by collisions of said particles and the toner particles to introduce random agitation of particles in the liquid and by the presence of the photoconductive particles in the photosensitive base, and the metallic particles in the carrier liquid of the developer, agitation is enhanced at the interface between the liquid and the photoconductor due to charge exchange between the fixed conductive particles in the photoconductor and the moving metal particles in the developer liquid, maintaining said body of developer itself quiescent except for the random particle movement, said toner particles being colored resin particles, said metal powders being selected from the group consisting of aluminum, bronze powder, zinc powder, aluminum powder, copper powder, intermetallic compound powder, tin powder, iron powder, and chromium powder. 
     
     
       2. The method of claim 1 in which said toner particles comprise a coloring medium in particulate form having a resin control coating on said particles formed by milling toner medium in the presence of a dissolved resin.